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The special skill of Pieris rapae crucivora climbing flight

Author

Yang, J. T.; Lee, C. Y.; Lee, B. H.; Soong, C. Y.

Abstract

In this work, we conduct a free-flight test to explore the climbing motion of a butterfly species (Pieris rapae crucivora) and find its excellent flapping skills in this maneuver. In regular flight, the downstroke of wing flapping generates most of the required lift force, while the upstroke results in less or negative lift. To produce continuous lift, however, the butterfly alters its attitude from supination to pronation in upstroke mode and turns it into a lift-generating stroke. The wingbeat kinematics and the associated flow field are visualized using a digital particle image velocimetry (DPIV) system. With the movie and the measured flow data, the velocity vector and the corresponding vorticity field near the flapping wing are analyzed in-depth. These results demonstrate an effective use of various vortical wakes and manifest the sophisticated wingbeat kinematics as well as lift-generating mechanisms in the climbing flight of the Pieris rapae crucivora.